Boolean Overlay

Boolean overlay is a spatial analysis technique that combines two or more binary (true/false) raster or vector layers using standard logical operators to produce a composite output. Each input layer classifies locations as either suitable (1) or unsuitable (0) for a specific criterion, and the overlay operation determines how these binary classifications are combined.

The AND operator (intersection) returns true only where all input layers are true, implementing the most restrictive combination: a location must satisfy every criterion to be selected. The OR operator (union) returns true where any input layer is true, implementing the most permissive combination: satisfying any single criterion is sufficient. The NOT operator (complement) inverts a layer, selecting locations that do not meet a criterion. XOR (exclusive or) selects locations that meet one criterion but not the other. These operators can be combined in complex expressions to implement detailed decision rules.

Land use planners use Boolean overlay to identify parcels that simultaneously satisfy zoningZoningZoning is a land use planning tool that divides geographic areas into zones with specific permitted uses, building st... requirements, slope limits, soil type criteria, and minimum distance from sensitive areas. Environmental regulators apply Boolean logic to delineate areas where development is prohibited based on overlapping protected zones. Emergency planners combine flood zone, evacuation route proximity, and building vulnerability layers to identify critical risk areas.

Boolean overlay is simple to understand, implement, and communicate. It produces unambiguous yes/no results that are easy to act upon. However, its rigid binary classification cannot represent partial suitability or gradual transitions. A location that barely fails one criterion is treated identically to one that fails dramatically, losing valuable nuance. For this reason, weighted overlayWeighted OverlayWeighted overlay is a raster analysis technique that combines multiple reclassified layers by assigning each a relati... and fuzzy logic approaches are often preferred for complex suitability analyses.